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Halley’s Comet

Five interplanetary spacecraft flew past the comet in March 1986: two Japanese spacecraft (Sakigake and Suisei), two Soviet spacecraft (
Vega 1 and
Vega 2), and a European Space Agency spacecraft (Giotto) that passed only 596 km [370 miles] from the comet’s nucleus. Close-up images of the nucleus obtained by Giotto showed a dark potato-shaped object with dimensions of about 15 × 8 km (9...

...informally known as the Halley Armada and consisted of two Japanese spacecraft, Suisei and Sakigake (Japanese for “comet” and “pioneer,” respectively); two Soviet spacecraft,
Vega 1 and 2 (a contraction of Venus-Halley using Cyrillic spelling); and an ESA spacecraft, Giotto (named after the Italian painter who depicted the Star of Bethlehem as a comet in a fresco painted...

Both
Vega spacecraft carried infrared spectrometers designed to measure the temperature of the Halley nucleus. They found quite warm temperatures between 320 and 400 K (47 and 127 °C [116 and 260 °F]). That surprised many scientists who had predicted that the effect of water ice sublimation would be to cool the nucleus’s surface; water ice requires a great deal of heat to sublimate. The...